The present invention relates to filters, and more particularly to a carbon block water filter for a water treatment system.
The use of home water treatment systems to treat tap water continues to grow dramatically in the U.S. and abroad, in part because of heightened public awareness of the health concerns associated with the consumption of untreated tap water. The most cost-effective conventional home water treatment systems typically use a carbon block filter to remove particulate matter and adsorb organic contaminants from a water stream. A conventional carbon block filter includes a mass of densely packed activated carbon particles that are bonded together to form a block through which untreated water can be filtered. As untreated water passes through this dense brick a combination of mechanical filtration and adsorption operate to remove a high percentage of particulate matter and organic contaminants from the water stream.
Carbon block filter manufacture can be complicated and typically involves a careful balance of various competing interests. It has been known that smaller carbon particles provide improved filtration. This is due in large part to the fact that smaller particles provide increased surface area and create a more dense block that traps smaller particulate matter. Unfortunately, smaller carbon particle sizes create several problems. First, water flow rates through the filter are dramatically affected. The dense block not only traps smaller particulate matter but can also greatly restricts the flow of water, significantly reducing the amount of water that can be treated in a given amount of time. Second, a high percentage of smaller carbon particles makes it difficult to manufacture the carbon block using conventional manufacturing techniques. More specifically, higher levels of fine particles interfere with the binder""s ability to make a solid carbon block. This causes cracking, crumbling and other defects in the carbon block, which in turn lead to low production yields. In balancing these concerns, conventional carbon block filter manufacturers typically use relatively large carbon particles in the manufacture of their carbon blocks. An alternative is to increase the level of binder contained in the block. Both of these practices generally increase production yields, while decreasing filter effectiveness. Typically, carbon block filters are manufactured from a standard 80xc3x97325 mesh carbon. Although the precise particle size distribution of standard 80xc3x97325 mesh carbon varies from manufacturer to manufacturer and from lot to lot, it typically includes a high percentage of +140 mesh carbon particles (i.e. particles that are larger in size than 140 mesh) and a small percentage of xe2x88x92325 mesh carbon particles (i.e. particles that are smaller in size than 325 mesh). A typical 80xc3x97325 mesh carbon usually has a mean particle diameter in the range of 98 microns or larger. As a result, filters manufactured from typical 80xc3x97325 mesh carbon generally provide relatively high productions yields and flow rate, but not exceptional filtration performance.
To increase filter performance at the expense of production yields and flow rates, another known carbon block manufacturer reduces the mean particle diameter of the carbon particles used to produce the block. To manufacture this carbon mixture, the carbon normally ground to form typical 80xc3x97325 mesh is subjected to a special grinding process that increases the level of carbon particles smaller than 325 mesh. Although the grinding operation inherently results in some variation, this modified carbon mixture generally provides a mean particle size of approximately 75 microns and a particle size distribution with approximately 25% or more of the carbon particles being larger than 140 mesh and 25% or more of the carbon particles being smaller than 500 mesh. Although the resulting carbon block filters provide improved performance, the high level of small carbon particles provides reduced flow rates and results in production losses of up to 20-30%. Further, the high level of small carbon particles produces carbon blocks that are relatively soft, making then susceptible to damage.
The aforementioned problems are overcome by the present invention wherein a carbon block filter is manufactured from a unique carbon mixture that provides a carbon block filter with improved performance, flow rates, hardness and production yields. The carbon mixture preferably including a mean particle diameter of about 60 to 80 microns and a particle size distribution of less than about 10% +140 mesh and less than about 10% xe2x88x92500 mesh. The carbon mixture is bonded together with a conventional binder to form an integrated carbon block. The carbon block can be incorporated into a wide range of carbon block filters in accordance with a variety of conventional techniques.
In a more preferred embodiment, the carbon block filter is manufactured from a carbon mixture having a mean particle size of about 65 to 75 microns and a particle size distribution of less than about 10% +140 mesh and less than about 10% xe2x88x92500 mesh.
In a most preferred embodiment, the carbon block filter is manufactured from a carbon mixture having a mean particle size of about 70 microns and a particle size distribution of less than approximately 7% +140 mesh and less than approximately 7.5% xe2x88x92500 mesh.
The present invention provides a carbon block filter that provides a reduced mean particle diameter and hence enhanced filtering performance over time. The carbon mixture also provides improved production yields. Further, the present invention provides a harder carbon block that is less susceptible to damage. Additionally, the present invention provides significantly improved flow rates over conventional carbon block filters with similar mean particle size.
These and other objects, advantages, and features of the invention will be readily understood and appreciated by reference to the detailed description of the preferred embodiment and the drawings.